1. Field of the Invention
The present invention is generally related to steering mechanisms for an outboard motor and, more particularly, to a steering mechanism that utilizes a rotary actuator disposed around the steering axis of an outboard motor.
2. Description of the Prior Art
Many different steering mechanisms are well known to those skilled in the art. In addition to manual steering with a tiller handle, several mechanical steering systems have been used. For example, it is common to use steel cables connected to both the outboard motor and a steering wheel to allow an operator to manually rotate an outboard motor about its vertical steering axis by turning a steering wheel. Hydraulic systems are also well known to those skilled in the art, in which a hydraulic piston exerts a force against a steering bracket to move an outboard motor about its steering axis. Various types of power steering systems also use hydraulic cylinders in this general way. Rotary actuators are well known to those skilled in the art and it is also known that rotary actuators can be driven either by hydraulic power or electrical power.
U.S. Pat. No. 4,422,366, which issued to Weyer on Dec. 27, 1983, discloses a rotary helical actuator. The helically splined hydraulic actuator is provided with hydraulic cushioning and rapid initiation of movement. The actuator is provided with an elongated cylindrical bearing integral with the shaft of the actuator for increasing radial and movement load-carrying capacity of the actuator without increasing its length.
U.S. Pat. No. 5,038,066, which issued to Pawlak et al on Aug. 6, 1991, describes a claw pole rotary actuator with a limited angular movement. The actuator has a permanent magnet ring with a plurality of radially magnetized poles rotatably positioned between a pair of toothed pole pieces with interdigitated teeth, an electromagnetic coil and pole elements coupling the coil flux to the pole pieces. The pole pieces may themselves be rotatable or stationary. The permanent magnet circuit attempts to move the magnet ring to a first position relative to the pole pieces, and the electromagnetic circuit, depending on the direction of current in the coil, torques the magnet in one direction or another toward stable positions on either side of the first position. The device is used as a two or three position actuator or as an actuator operating against an external force and seeking a position as a function of current.
U.S. Pat. No. 3,426,652, which issued to Blake on Feb. 11, 1969, describes a rotary hydraulic actuator with locking means. A rotary fluid actuator in which a rotor is mounted coaxially with a pressure cylinder with an annular pressure chamber extending around the rotor and divided into subchambers by vanes rigidly mounted on the rotor and cylinder. A fail-safe locking means carried by the rotor automatically locks the rotor against rotation within the cylinder upon the absence of fluid pressure within the annular pressure chamber. Application of fluid pressure tending to rotate the rotor releases the locking means.
U.S. Pat. No. 3,587,511, which issued to Buddrus on Jun. 28, 1971, describes a hydraulic marine propulsion system. The hydraulic propulsion system features an inboard power plant and fluid pressure-generating system and an outboard fluid driving system. The inboard pressure-generating system consists of a reversible variable displacement axial piston pump, a lever-operated servosystem, a speed control, a charge pump, and valve manifold units. The outboard fluid-driving system consists of a fixed displacement axial piston fluid motor and propeller.
U.S. Pat. No. 3,847,107, which issued to Buddrus on Nov. 12, 1974, describes a hydraulic marine propulsion and guidance system. The propulsion and guidance system consists of a fluid pressure generating system and a helm pressure generating unit located within the vessel. It also comprises a tilting fluid actuator mounted to the transom of the vessel, a lift clevis operatively connected to the shaft of the tilting actuator, a rotary fluid actuator mounted within the lift clevis, a steering clevis operatively connected to the shaft of the rotary fluid actuator, a fluid motor-propeller assembly secured to the steering clevis, an additional fluid pump located within the vessel and fluid conduit operatively connecting it to the tilting actuator such that as the pump is operated the shaft of the tiled actuator rotates the lift clevis in turn tilting the fluid motor-propeller assembly. It further comprises fluid conduit which operatively connects the helm pressure generating unit and the rotary actuator such that as the helm pressure generating unit is operated the shaft of the rotary actuator rotates the steering clevis and the fluid motor-propeller assembly. The fluid conduit includes single passage oscillating swivels mounted to the transom along a common axis defining the center of rotation of the lift clevis. The system further comprises fluid conduit which connects the fluid pressure generating system and the fluid motor including a multiple passage oscillating swivel operatively mounted to the steering clevis and aligned with respect to the axis of rotation of the steering clevis. The swivels permit the use of rigid fluid connections throughout the system.
U.S. Pat. No. 3,673,978, which issued to Jeffery et al on Jul. 4, 1972, discloses an outboard drive unit for boats. An outboard propulsion drive unit for a boat with an inboard engine utilizes a hydraulic pump on the engine hydraulically connected with a universal swivel mounting which receives an outboard propulsion unit to provide steering about a generally vertical axis and up-tilt motion about a transverse horizontal axis. The swivel mounting has a pair of hydraulic conduits extending through the bearing journals of both axes. The propulsion unit has a hydraulic motor geared to drive the propeller. A reservoir and a charging pump are mounted in the propulsion unit, the latter being driven by the hydraulic motor.
U.S. Pat. No. 3,596,626, which issued to Buddrus on Aug. 3, 1971, describes a steering and tilting system for marine vessels. The steering and tilting systems feature hydraulic actuators. The steering system comprises two self-contained units including a first helm pressure generating assembly positioned as desired within the vessel and a second hydraulic rotary actuator assembly suitably mounted to the vessel guidance system. The tilting system also comprises two self-contained units including a first motor driven hydraulic pump positioned as desired within the vessel and a second hydraulic actuator assembly suitably mounted to the underwater propulsion system.
Many different types of rotary actuators are known to those skilled in the art. The Helac Corporation provides a series of hydraulic rotary actuators. These hydraulic rotary actuators can be of the helical rotary actuator type or the planetary hydraulic rotary actuator type. Various types of helical shaft actuators, helical pivot actuators, ball bearing actuators, and planetary actuators are available in commercial quantities.